Rotary grinding mill



Feb. 16, 1965 3,169,71 l

R. D. HELMS ROTARY GRINDING MILL Filed April 16, 1963 INVENTOR.

B05597- B H54 MS United States Patent 3,169,711 ROTARY GRINDING MILLRobert D. Helms, 939 Arcadia Ave., Arcadia, Calif. Filed Apr. 16, 1963,Ser. No. 273,364 6 Claims. (Cl. 241-74) This invention has to dogenerally with improvements in rotary grinders of the hammer mill type,usable for comminuting any of various materials, typically of vegetableorigin and in the category of feeds and the like. More .specifically,the invention relates to grinders'of this type comprising an impactelement or hammer assembly rotatable at the inside of a screen againstwhich the hammers impact to reduce the material for passage through thescreen.

My general object is to provide improvements in such grinding equipmentthat permit greatly increased throughput in relation to powerconsumption, by comparison with conventional grinders, and whichotherwise have advantages in permitting construction of the equipmenteconomically and according to highly practicable designs.

structurally considered, the invention achieves its important objectivesby reason of a novel screen assembly which provides for full circularscreen extent about the rotor assembly, with consequent increasedcapacity for continuous comminution of the feed material and passage ofthe fines through the screen, together with a separable end screenwhich, though not receiving the hammer impact, presents an addedforaminous medium for the passage of fines displaced beyond the impactarea of the hammers.

Accordingly, the invention contemplates accommodation of a ring screenabout the hammer rotor-and in communication at one end with a feedopening, and detachably secured at its opposite end to a disc screen,separability of the two screens being of advantage in permittingreplacements only of the ring screen which is subject to most severewear.

As will appear, the invention further contemplates providing for one endof the grinder housing a removable closure provided with means capableof manipulation at the outside to bear against the end of the discscreen, and in so doing to retain the screen assembly in operatingposition by pressing the opposite end of the ring screen against theinlet end of the housing. Thus in addition to maximized screen areaabout and beyond the hammer assembly, the invention provides for easyassembly and dismantling of the grinder parts as required from time totime for replacement or screening purposes.

The invention has various additional features and objects, all of whichwill be most readily understood from the following detailed descriptionof an illustrative embodiment shown by the accompanying drawing inwhich:

FIG. 1 is a view showing the grinder in front elevation, a portion ofthe chamber closure being broken away to expose the interior;

FIG. 2 is a vertical cross section taken on line 2-2 of FIG. 1; and

FIG. 3 is a perspective showing of the screen assembly.

The grinder structure is shown generally to comprise a housing defininga grinding chamber 11 and having a removable front closure 12 for thechamber access opening 121, the chamber containing a grinder rotor 13within a screen assembly 14 into which the material 15 to be ground isfed from chute 16.

Merely as exemplary, the housing 10 is shown to be peripherally definedby an imperforate octagonal wall 17 closed at its rear by plate 18 whichmounts and may form the front wall of chute 16, plate 18 containing afeed opening 19 through which the material 15 feeds into the screenassembly 14, under control of a valve or gate 20 manually positionableby lever 21.

The chamber closure 12 is shown to be conformed in shape with the wall17 and releasably held thereto by bolts 22 pivoted to the housing at 23and extending through the bifurcations of projections 24 carried by theclosure. The latter is releasably held to the housing by nuts 25threaded to bear against the projections 24.

Rotor 13 may be of any appropriate type or construction capable of.comminuting the feed material against the screen structure. Merely asillustrative, the rotor is shown to comprise circularly spacedassemblages of hammer pieces 26 pivoted at 27 to hub plates 28 on therotor shaft 29 driven by motor 30.

The invention is primarily concerned with the screen assembly 14 whichis shown to comprise a cylindrical or ring section 31 removably retainedin concentric relation with the rotor, within ring flange 32 fixed toplate 18. The assembly 14 also includes a disc screen 33 to which iswelded spaced bar stock rings 34-3411. between which is received theouter end of the ring screen 31. Suitable fasteners, such as set screws35, may be provided for releasably holding together the screens duringtheir installation and independently of the chamber end closure.

Provision is made for releasably retaining the ring screen within flange32 by threading through the closure plate 36 circularly arranged screws37, the inner ends of which carry pads 38 which may be pressed againstthe screen disc 33 to retain the screen assembly in the conditionillustrated by FIG. 2.

In the operation of the grinder, the rotor hammers 26 impact against andcomminute the feed material against the ring screen, causing passage ofthe fines through the screen into chamber 11 for appropriate removal asthrough outlet 39. Rotation of the hammer assemblies tends to displacesome of the material being ground, up-

wardly about the rotor and opposed surfaces of the ring screen, so thatthe latter remains effective for' the full 360 grinding surface and forpassage of fines throughout the full circular extent. By virtue of theremovability and adjustability of the screen ring, the latter may berotationally varied to expose different arcuate extents to the moresevere grinding action at the bottom, and for such purposes the screenmay be reversed to bring either end within the retaining flange 32.

The disc screen 33 presents an additional foraminous medium for thepassage into chamber 11 of fines displaced outwardly beyond the rotorand opposite its full circular extent. Being subjected to greater wearthan the disc screen, the ring screen 31 may be replaced a number oftimes during the useful life of a single disc screen. As will beapparent, by the simple procedure of removing the cover plate 36, accessmay be had to chamber 11 for cleaning, readjustment or replacement ofthe screen parts.

I claim:

1. A grinder comprising a housing having an imperforate wallperipherally defining a grinding chamber and having at the front end ofthe housing an access opening and at its rear end a feed opening, amovable closure for said access opening mounted to the front end of thehousing, a rotatably driven shaft and radially movable hammer assemblywithin said chamber, a screen ring surrounding the said assembly andinternally communicating at one end with said feed opening to receivematerial to be ground by said assembly against and passed through thescreen, said screen being annularly spaced from said imperforate housingwall and the space cornmunica-ting with an outlet passage at the baseof. the housing, a second screen removably engaged against the oppositeend of the screen ring directly at the inside of being removable throughsaid access opening of the lions ing when said closure is opened. r 2. Agrinder according to claim 1, in which said sec- 1 .ond screen is'incentrally continuous disc'form fitted to the screen ring and'ispositioned beyond the 'end of the shaft and harnmer assembly. 1

3. A grinder according to claim 2,' including fastenors directly andreleasably interconnecting'said screens.

4. A grinder according to claim 1,'including bearing means carried bysaid closure and bearing agalnst said second screen and pressing thescreen ring against said positioning means'about said feed opening. 5. Agrinder according to claini 4, in which said bearing' means compriseretainers threaded, through I said closure and carrying terminal padsengageable against said second screen; a

' 6. A grinder according to claim 1, in which said second screencomprises a screen disc fitted and detachably secured to said oppositeend of the screen ring, and including also retainers threaded throughsaid closure and c'arrying'terminal pads bearing against the disc screenand pressing the screen rin'g against the housing about said feedopening.

References Cited B the Examiner ANDREW R. JUHASZ, WrLLrAM w. DYER,

' Examiners.

1. A GRINDER COMPRISING A HOUSING HAVING AN IMPERFORATE WALLPERIPHERALLY DEFINING A GRINDING CHAMBER AND HAVING AT THE FRONT END OFTHE HOUSING AN ACCESS OPENING AND AT ITS REAR END A FEED OPENING, AMOVABLE CLOSURE FOR SAID ACCESS OPENING MOUNTED TO THE FRONT END OF THEHOUSING, A ROTATABLY DRIVEN SHAFT AND RADIALLY MOVABLE HAMMER ASSEMBLYWITHIN SAID CHAMBER, A SCREEN RING SURROUNDING THE SAID ASSEMBLY ANDINTERNALLY COMMUNICATING AT ONE END WITH SAID FEED OPENING TO RECEIVEMATERIAL TO BE GROUND BY SAID ASSEMBLY AGAINST AND PASSED THROUGH THESCREEN, SAID SCREEN BEING ANNULARLY SPACED FROM SAID IMPERFORATE HOUSINGWALL AND THE SPACE COMMUNICATING WITH AN OUTLET PASSAGE AT THE BASE OFTHE HOUSING, A SECOND SCREEN REMOVABLY ENGAGED AGAINST THE OPPOSITE ENDOF THE SCREEN RING DIRECTLY AT THE INSIDE OF SAID CLOSURE, AND MEANSPOSITIONING THE SCREEN RING TO THE HOUSING ABOUT THE FEED OPENING, SAIDSCREEN RING BEING RELEASABLE FROM SAID POSITIONING MEANS AND THE SCREENSBEING REMOVABLE THROUGH SAID ACCESS OPENING OF THE HOUSING WHEN SAIDCLOSURE IS OPENED.